在WPF文本框中显示XML

protected string FormatXml(string xmlString)
    {
        XmlDocument doc = new XmlDocument();

        doc.LoadXml(xmlString);

        StringBuilder sb = new StringBuilder();

        System.IO.TextWriter tr = new System.IO.StringWriter(sb);

        XmlTextWriter wr = new XmlTextWriter(tr);

        wr.Formatting = Formatting.Indented;

        doc.Save(wr);

        wr.Close();

        return sb.ToString();
    }